1. Field of the Invention
This invention relates to the field of wafer processing in the manufacture of semiconductor devices and more specifically to a method for containing the wafer in a specified area on the processing line.
2. Prior Art
During the processing of semiconductors, wafers are used from which many devices are formed. It is sometimes desirable to subject these wafers to heat, apply a coating, and then to cool them down. In the prior art this is accomplished by resting the wafer on a hot plate and heating it to the desired temperature, applying the coating to the wafer, and then transporting the wafer to a cooling plate in order to return it to ambient temperature. These plates typically are smooth surfaces containing holes in the upper surface from which air is propelled to assist in moving the wafer from one plate to another. In order to prevent the wafers from falling off the plates, and to keep them generally disposed in the center of the plates, wafer guides are employed. These guides are typically a pair of teflon bars, one bar on each side of the plate and of sufficient thickness such that a wafer contacting the guide will be restrained from lateral movement off the plate.
There are several disadvantages associated with prior art wafer guides. First, the guides are straight, and because of different processing needs, are placed at varying distances from the edge of the plates on which they are used. When a wafer moves from a plate with widely spaced guides to a plate with more narrowly spaced guides, the wafer can get stuck or slowed at the leading edge of the narrower guides. Second, when the wafer comes in contact with the guide, microcracks and microfractures are formed in the wafer. These cracks are too small to be detected by eye, but result in reduced yield of the wafer.
It is an object of the present invention to solve both of the above disadvantages by a simple yet effective solution.